1. Field of the Invention
This invention relates generally to the removal of contaminants from soil, sand, etc., and more particularly to improved volatilization equipment.
2. Description of Related Art
A vast number of sites have been identified in which the soil has been contaminated by gasoline leaking from underground tanks, dumped oil or other sources. It is recognized that these contaminants will eventually make their way to the ground water. To reduce this source of water pollution, large quantities of soil containing these contaminants must be removed and either treated to remove the contaminants or stored safely. Storing such soil can be no more than a temporary expedient.
My previous invention entitled "Reflux Volatilization System", Ser. No. 07/194,203, filed May 16, 1988, was an effective and economical system for removing volatilizable contaminants from soil. Further consideration of this problem has resulted in a system having enhanced capability. One area which is improved pertains to the logistics of such a system. Because the system feeds back heat produced during decontamination to decrease the use of fuel for heating, it is most efficiently run as a continuous operation. The soil or other material which is to be treated is typically delivered to the treatment site by trucks which do not always arrive on a regular and predictable basis. Therefore, the addition of large capacity holding bins permits the system to be operated continuously even when the trucks experience long delays.
A second major area of improvement relates to the volatilizer. In the previous system, a counterflow arrangement was used in which hot gases were introduced at one end of a volatilizer and the unheated soil was introduced at the other end. In the present system, two volatilizers arranged in series are used, with the second volatilizer burning at least seventy five per cent of the vaporized hydrocarbons released in the first volatilizer.